The present invention relates to a programmable device and, more particularly, to a memory module for a programmable device.
Recently, many programmable devices have been proposed such as a programmable electronic calculator, a personal computer, and a word data processing device such as a word processor and a language dictionary. To these programmable devices, a read/write memory (RAM) or a read-only memory (ROM) module is connected which stores a program for the programmable devices to execute the program. Any program can be entered into the RAM module by operation of key switches by the operator. The ROM module stores the program, preliminarily, prior to the operation by the operator. Since the widely sold ROM modules are directed to general purposes, a specific program appropriate to a specific programmable device is not recorded. To make the programmable devices specific to the operator, the RAM module would be preferred to the ROM module because a new program can be stored into the RAM module by operating the key switches.
However, the stored program in the RAM module may be damaged by erroneous key input operations. In such a case, the program input must be repeated from the beginning.
Therefore, it is desired that the RAM module is prevented from being damaged even by misoperating the key switches.